First Author: S.Silva PORTUGAL
Co Author(s): F. Braz I. Silva H. Nogueira
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Purpose:
To analyze the changes in astigmatism parameters induced by phacoemulsification with small incision changes between the first 1 month and at least 9 months after surgery.
Setting:
: Instituto de Oftalmologia Dr. Gama Pinto, Lisbon, Portugal
Methods:
The medical records of all patients undergoing phacoemulsification, performed by the same surgeon and without uneventful events, we analyzed retrospectively, between January 2008 and December 2009.
All procedures for cataract extraction surgery were performed using the same technique: phacoemulsification with clear cornea incision and implantation of an intra-ocular lens in the capsular bag (AMO ® AR 40 monofocal lens). A 2.75 mm keratome for the main incision and a 15° stab knife to the ports of entry were used.
The incisions were temporal superior in right eyes and nasal superior in left eyes (oriented along the axis of 100 degrees).
Only cases with autokeratorefractometer (KR-8800®) records in the first month and at least 9 months after surgery were analyzed.
Outcome measures included cilindric axis and cilindric power mesured by the autokeratorefractometer.
We excluded all patients with know corneal pathology.
Results:
41 eyes of a sample of 18 men and 23 women were analyzed with a mean age of 74±6,8 years.
The last evaluation (closest to a minimum of 9 months after surgery) was performed on average at the end of 14.36 months.
In the first month after surgery, most of the astigmatism cases analyzed (48.6%) were against-the-rule (ATR), the mean axis of astigmatism was 88.6±41.5 degrees with an average power of -1.28 D.
At the end of the analysis period, most of the astigmatisms recorded continued to be of ATR type (55%), the mean axis of astigmatism was 95,86 ±35,7 degrees with an average power of astigmatism was -1.16 D.
In the analysis of the type of astigmatism, cases with initial: ATR astigmatism, in 66.6% showed the same type of astigmatism; oblique astigmatism, in 50% showed the same orientation and 42% suffered a variation to ATR; WTR astigmatism, in 40% suffered a variation for the ATR type and 40% kept the same orientation. In 52,7% cases the astigmatism axis changed more than 10 degrees during the follow up period after surgery. The axis changed on average 22.4 degrees and in most in a counterclockwise direction.
Conclusions:
By the analysis of our sample, corneal residual astigmatism induced by vertical incisions undergoes changes in the axis of at least 10 degrees in a considerable number of patients (52,7%) after a mean follow up period of 14 months. Most axis of cylindrical errors changed to an ATR subtype.
Surgeons should consider in the operative plan of cataract surgery, not only the best strategy to reduce the total preoperative astigmatism, but also how the final residual astigmatism continues to change.This analysis supports an additional reason to perform horizontal incisions in candidates with a pre-existing corneal astigmatism of the ATR type.
Financial Disclosure:
No"
